1. Field of the Invention
The present invention, in general, relates to electrical connectors and, more particularly, to electrical connectors that are suitable for use in challenging environments.
There are many situations in which a connector must maintain connectivity and permit rapid disconnection when required while dealing with specific environmental challenges.
One such example occurs at oil and/or gas wells. It is necessary to supply electrical power to pumps and other electrical equipment that are disposed in oil and gas wells. The electrical connection occurs through the top of the well, commonly referred to as the “wellhead.” Typically, an electrical cable is used to supply the requisite electrical power to the wellhead.
According to a prior art solution, attached to a proximate first end of the electrical cable is a first half of a prior art type of an electrical connector. The first half of the prior art electrical connector is attached by screw threads to a corresponding second half of a prior art type of an electrical connector. The second half of the prior art electrical connector is attached to a feed-through disposed in the wellhead. The feed-through provides a physical connection that is mechanically secured to the wellhead and it also provides an electrical connection that interfaces at the top with the conductors of the cable and at the bottom with the conductors of an inner cable that is disposed in the well and which extends down the well to the pump or other equipment that is disposed inside of the well.
The prior art first half of the electrical connector (which is attached to the cable) includes inside screw threads and a plurality of electrical sockets. The prior art second half of the electrical connector includes outside screw threads and a plurality of electrical pins that mate with the electrical sockets.
There are various times when it becomes necessary to disconnect the electrical cable from the wellhead, for example, when servicing the pump or other equipment that is disposed in the well. A standard procedure exists for disconnecting the electrical cable from the wellhead which requires that electrical power first be removed from the cable prior to any attempt to physically disconnect the cable from the wellhead.
A circuit breaker or other type of electrical switch that supplies electrical energy to a distal second end of the cable is turned off at a location remote from the wellhead. After ensuring that electrical power is not supplied to the cable, an operator will begin to unscrew the first half of the electrical connector apart from the second half of the electrical connector. The process of removing the first half of the connector from the wellhead takes a considerable amount of time and the lessening of this time is an important object of the instant invention.
The ambient environment proximate the well can be potentially explosive. Volatile ambient gases and a quantity of oxygen may be present and comingle in proportions that could combust, if ignited. Although very unlikely, it is possible that these gases could enter into the electrical connector during disconnection and, if ignited, result in an undesired forced separation of the connector halves and possibly even an igniting of the surrounding ambient atmosphere.
This type of an environment as well as other similar environments is sometimes referred to in the electrical connector industry as being either hazardous or potentially explosive.
Electrical connectors used in such an environment are frequently required to be certified as compliant to an appropriate standard, for example, to a relevant part of the National Electric Code (NEC), by any of the various testing agencies that verify compliance with domestic and/or international standards for use in hazardous environments. The testing and verification of the compliance of electrical connectors with a particular standard is well-known throughout the world and is not discussed in detail herein.
The particular standard that the electrical connector needs to comply with depends on where the connector is to be used. For example, ATEX approval is required for use in Europe whereas certification to ensure NEC compliance is required for use in the U.S. IEC also provides standards that are relevant to electrical connector design.
An electrical connector that is compliant with the above NEC standard is typically referred to as being an “explosion proof” type of connector whereas if the electrical connector were compliant with the above ATEX standard it would typically be referred to as a “flame proof” type of connector. Other generic language, such as the electrical connector being suitable for use in a “hazardous location” may also be included as a part of any particular standard or other generic language may be used by those who are skilled in the electrical connector arts when referring to these types of electrical connectors.
The instant invention is intended to meet or exceed the above certification standards as well as any other applicable industry standard, domestic or international, governing any class, category, or rating for which the instant electrical connector can be used or modified for use. As is discussed in greater detail herein, it is expected that the broader teachings disclosed herein will be modified and adapted to provide electrical connectors with advantages and improved performance capabilities that are suitable for use in a variety of applications and environments not specifically mentioned herein. In general, all versions and modifications of the instant invention are expected to be designed to meet the governing standards for the application at hand.
What is especially significant to note is that prior types of electrical connectors which have been able to satisfy the appropriate standards for use in a hazardous or potentially explosive environment have all relied on a screw thread type of connection between the electrical connector halves. There has previously been no known way to provide an electrical connector for use in a hazardous or explosive environment, such as at an oil wellhead, that includes a bayonet type of connector and which is able to comply with the applicable standards governing use in a hazardous or explosive environment.
Most of the generally accepted industry standards that an electrical connector is required to comply with if it is used in a hazardous or explosive environment also require the electrical connector to contain combustion that may occur within the electrical connector, however unlikely that may be, within the confines of the electrical connector itself. In this way any combustion that might occur in the electrical connector is prevented from reaching the ambient atmosphere which surrounds the electrical connector.
It is unlikely that the atmosphere which surrounds the electrical connector would also contain a combustible or a potentially explosive mixture of gases and, if it did, that such a condition would not be detected by the operator. Because it remains a possibility, however remote, the applicable standards for use in a hazardous or potentially explosive environment are designed to help prevent combustion of the ambient environment from occurring as a result of any unlikely combustion occurring in the electrical connector during a disconnection of the two connector halves.
In the relevant electrical connector industry, the propagation of combustion (i.e., of a flame) from its point of origin in the electrical connector which travels to a location that is remote from the point of origin, such as to the ambient atmosphere or to another location within the electrical connector, occurs along what is commonly referred to as a “flame path”. The design of prior art electrical connectors for use in an explosive or hazardous environment have found that by controlling certain tolerances along a potential flame path it is possible to limit the extent of propagation of combustion occurring inside the connector.
This has been accomplished with prior art electrical connectors by the simultaneous control of two important tolerances. The ability to control these two tolerances has not heretofore been possible with a bayonet type of connection and this inability is a significant reason as to why all prior art electrical connectors for use in a hazardous or explosive environment have relied upon screw threads. Another prior art reason for using screw threads in these environments relates to mechanical strength, and this is discussed in greater detail below.
It has been determined that by restricting a gap tolerance between the cooperating screw threads to an amount which is equal to or less than a maximum gap tolerance between the cooperating screw threads while also ensuring that that the maximum gap tolerance is maintained for at least a predetermined length, that the continued propagation of combustion along the flame path is stopped.
To accomplish the above safety requirements for use in an explosion-proof environment, a careful machining of predetermined areas of the first half electrical connector and second half electrical connector is required such that there exists both appropriately limited diametrical clearances on any non-threaded features as well as appropriately machined (pitched) threaded areas.
As an example, an “Explosionproof” connector adhering to the NEC CLASS 1 DIVISION 1, GROUP C standard (as defined by standard FM 3615) would be:
“ . . . enclosed in a case which is capable of: 1) withstanding an internal explosion of a specified gas or vapor-in-air atmosphere; 2) preventing the ignition of a specified gas or vapor-in-air atmosphere surrounding the enclosure due to sparks, flashes or internal explosion; and 3) operate at temperatures which will not ignite the surrounding atmosphere . . . . ”
By limiting the above predetermined flame path areas per their respective specifications, any flame arising from a combustion occurring inside the connector that would attempt to propagate along a potential flame path as provided by the predetermined diametric clearance area or the screw threads (i.e., a mating of the first half electrical connector and second half electrical connector) would be extinguished by any travel that is over 6 mm or five threads respectively. Accordingly, the flame would not be able to reach the ambient environment providing the first half electrical connector and second half electrical connector remain attached to each other.
The rapid increase in pressure that occurs as a result of combustion inside the electrical connector would exert a substantial force on the first half of the electrical connector attempting to separate it from the second half electrical connector. Separation prevention is provided by the previously cited minimum five threads of engagement (and by a snap ring that affixes the threaded coupling nut to the remainder of the first half electrical connector). Prudent safety factor engineering dictates that at least five threads of engagement between the first half of the electrical connector and the threads of the second half of the electrical connector be present at the moment of final electrical separation between the last of the contact power pins from its corresponding socket due to the probability that a spark may occur at this specific point during the separation.
Maintaining five revolutions of screw thread engagement is also helpful in providing the mechanical strength of connection necessary to retain the connector halves together in the unlikely event of an explosive type of combustion occurring in the electrical connector during separation of the connector halves.
Together, the need to contain propagation of the flame within the electrical connector and the need to provide sufficient mechanical strength and a type of mechanical connection that can prevent unwanted forced separation of the connector halves from occurring has compelled all prior electrical connectors that are designed for use in a hazardous or explosive environment to rely upon a screw thread connection between the electrical connector halves.
Of course, the entire connection or disconnection process of the electrical connector with respect to the wellhead is accomplished by the operator while also relying closely on a detailed connection and disconnection procedure that has been developed to further improve safety. In this manner, the likelihood of ignition occurring during disconnection of the electrical connector is highly unlikely.
Additionally, the established procedures for the operator also help to ensure that during connection the first half of the connector is fully and properly mated with the second half while also helping to ensure that the electrical connector is not over tightened.
A common method of determining that the first half of the electrical connector is fully mated to the second half includes a marking that is provided on the second half. The marking is obscured to some degree when the first half is fully tightened to the second half. In some installations it may be difficult or impossible to observe the marking. Therefore, it is possible for the operator to either over tighten or under tighten the first half of the electrical connector with respect to the second half of the electrical connector. It is also important to note that the operator does not receive any clearly discernible tactile or audible indication regarding installation when using any of the prior art types of explosion-proof electrical connectors.
It is important to note that for other potential uses of the instant electrical connector, such as for any particular application or environment other than that described herein for a preferred embodiment appertaining to use in oil and/or gas wells, that the standard or standards which regulate the dimensions or tolerances of the preferred embodiment are, of course, no longer utilized. For other applications, the dimensions and tolerances (and all other attributes) of the electrical connector are modified to comply with the requirements of the application at hand and the requirements of any applicable governing standard.
Heretofore, there has been no known way to overcome the above limitations associated with prior art electrical connectors for use in a hazardous or explosive environment that rely on a screw thread connection nor has there been any way to adapt a bayonet connector for use in such an environment.
It is especially important to note that the instant electrical connector is able to comply with standards (such as for use in a “hazardous location”) that no previously designed bayonet type of electrical connector has been able to meet.
It is also to be understood that the instant invention can be modified for use in other environments, for example in environments that are not as severe as those described herein or, alternately, in environments that are even more severe or demanding. Those having ordinary skill in the electrical connector arts after having had benefit of the instant disclosure will be able to modify tolerances or other characteristics, as needed, to permit use of the instant invention in a variety of applications that stand to benefit the advantages and benefits that are provided by the instant invention.
The above critical application requires both flame path attenuation and prevention of an undesired forced separation of the connector halves from occurring in the event of an unwanted condition, such as combustion inside the connector. The instant invention provides these capabilities in a bayonet type of connector that can be modified to provide additional benefits and capabilities.
For example, there are applications where a bayonet connector would provide advantages over other types of connectors, for example, those that attach with screw threads where flame path attention is not a need, however, where there is a strong need to maintain connectivity even in the unlikely event of an inadvertent release of the bayonet connection. Applications that may subject the electrical connector to high levels of vibration pose a risk of inadvertent release as would also occur when there is a possibility of inadvertent contact by the connector with human or other traffic or by objects that might rotate the connector from a secured position into a loosened position.
Applications in the aerospace industry or military applications may similarly benefit from an electrical connector that maintains electrical connection even if it is inadvertently loosened. Such an electrical connector would also need to resist further loosening. Ideally, if such an inadvertent loosening were to occur, the electrical connector would provide indication, such as by a severed contact between a pin and a socket thereof, to provide an alert that an inadvertent separation had occurred.
A bayonet type of electrical connector that is able to provide any of the above-described benefits would represent an improvement over the current state of the art, including prior art screw thread types of electrical connectors and prior art bayonet types of electrical connectors.
While many of the above-described applications include a first half of an electrical connector that is attached to a cable and a second half of the electrical connector that is attached to an object, such as to the wellhead or to an instrument or other type of panel, there are also applications where one cable can be attached to another cable that can similarly benefit if a suitable bayonet type of connector is available. The instant invention is anticipated to be modified for use in a wide range of applications that can include attaching a cable to another cable or attaching a cable to a panel, instrument, or other device and for use in any conceivable environment.
Accordingly, there exists today a need for a bayonet connector that helps to ameliorate the above-mentioned problems and difficulties as well as ameliorate those additional problems and difficulties as may be recited in the “OBJECTS AND SUMMARY OF THE INVENTION” or discussed elsewhere in the specification or which may otherwise exist or occur and are not specifically mentioned herein.
Clearly, such an apparatus would be a useful and desirable device.
2. Description of Prior Art
Electrical connectors are, in general, known and have been described hereinabove. While the structural arrangements of the above described and known types of devices may, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.